1. Field of the Invention
The field of the invention relates generally to methods of feeding media from a media input area of an image forming device, and, in particular, to correcting media feeding errors using separator roll position or separator roll rotational speed.
2. Description of the Related Art
Image forming devices, such as printers, scanners and photocopiers utilize media feed mechanisms for feeding various types of media sheets into the image forming devices. Examples of the various types of media sheets include, but are not limited to, printing paper, bond paper, coated paper, fabrics, transparencies and labels. Almost all of the media feed mechanisms include a pick roll that feeds a media sheet into the image forming device for further processing. In a media feed mechanism, various arrangements of the pick roll may exist for feeding the media sheet into the image forming device.
Image forming devices typically include multiple input sources to introduce the media sheets into the media path. The input sources may accommodate a range of media types and a range of media sheet quantities from a single media sheet to large quantities such as 2,000 or more sheets. One type of input source is referred to as a removable media input tray (“removable media input tray”) integrated within the same housing that contains the imaging units of the image forming device. A multi-purpose feeder may also be provided on the image forming device housing or as part of the integrated media tray for accommodating a low number of media sheets and often for specialty media sheets that are difficult to feed through normal input trays, such as envelopes, transparencies, and cardstock.
Another input source is referred to as an option assembly typically comprising a housing and a removable media input tray that is slidably received into the option housing. These option assemblies are typically stackable allowing one or more option assemblies to be used with a single image forming device which is typically positioned on top of the uppermost option assembly in the option assembly stack. Typically each option assembly may contain a different type of media such as letterhead or a different size such as A4 or a larger quantity of the same media type that is found in the integrated removable media input tray.
Each option assembly provides an extension to the media path of the image forming device and may provide one or more additional branches or avenues for introducing media into the media path of the image forming device. The media path extension extends from the top to the bottom of each option assembly and is upstream of the media path in the image forming device. When another option assembly is positioned below an option assembly, the media path extension permits media in the lower option assembly to be fed through the upper option assembly and into the media path of the image forming device that extends at its upstream end through the front portion of the integrated media tray. To accomplish the feeding of media either from a removable media input tray in an option assembly or from another option assembly, feed rollers have been provided in each option housing and in the media path extension to receive picked media either from a lower or inferior option assembly removable media input tray or from its own adjacent removable media input tray.
Included in each option assembly are a pick mechanism for moving media from the media tray, a media positioning mechanism and one or more drive motors for powering the pick mechanism, media positioning mechanism, and one or more adjustable media restraints such as a side restraint and a rear restraint to accommodate for different media widths and lengths. Further included are media sensors for determining when media is present in the tray, the size of the media and/or the location of the leading and trailing edges of the media.
Media trays have a media dam integrally formed in their front wall that is used to help direct the fed media into the media path. Typically such media dams are at an obtuse angle to the direction of the initial movement of the media being picked. Media dams are known to include wear strips on their front or face. Wear strips are slightly raised surfaces on the front face extending vertically along the surface of the media dam in contact with the picked media and help to decrease friction and aid in corrugating the fed media. Separator rollers are typically provided downstream of the media dam within the housing of the option assembly above the removable media input tray or in the image forming device above the removable media input tray therein. The separator rollers usually include a pair of opposed rollers, forming a nip therebetween, driven in the same direction so that one roll stops misfed sheets while the other allows a topmost sheet to be fed. They are used to reduce the chance of media misfeeds such as multiple feeds and shingling.
A common problem in feeding a top or bottom sheet of media from a stack of media sheets is that the sheet being fed may stick together with at least one of next adjacent sheets and may be fed together at the same time. This problem is worse when feeding difficult-to-feed special media such as cardstock and labels. Labels are formed on a thick medium with numerous ridges and valleys that interlock from one sheet to the next, causing the sheets to stick together. Also, certain label materials, such as vinyl, tend to stick together.
The separator rolls may be in opposed pairs or may be unopposed rolls. In either case, a roll is mounted behind the media dam and has a portion projecting through the dam and out into the media path. A higher height would be more optimum for special media such as cardstock, envelopes, and labels, for example, while a lower height would be more optimum for the light weight media, such as onion skin, or sheets having a low intersheet friction such as bond or xerographic paper (collectively referred to as “light weight media”). The separator roll rotates counter to the media feed direction. When two sheets are fed by the pick mechanism from the media tray in a shingled manner, the top sheet hits the separator roll in a glancing manner and is driven by the pick mechanism up over the surface of the separator roll to continue along the media path. The lower or second sheet hits the separator roll more directly and is stopped.
In some instances, separator rollers of one type are changed out to another type depending on media type to be fed from the media tray. Because of their downstream location in the housing, this is at times an awkward process. To help with this problem, media dams that include the separator rollers that project a set distance out from the media dam and into the media path and that are removably mounted in the media tray have been created. Such removable media dams are easily uninstalled and reinstalled by a user, easily changed the type and configuration of the separator rolls. However such removable media dams have one drawback in that for a given media dam the amount that the separator rolls project into the media path is fixed. This means that a media dam configured for one type of media, such as lightweight media, would not be suitable or not reliably separate heavier weight media. This leads to the problem of whether to have a height of the separator rolls optimized for reliably separating heavy weight media or to have a height of the separator rolls optimize for reliably separating light weight media. Accordingly, users would have a variety of removable media dams available to handle different types and weights of media.
It would be advantageous to have a removable media dam where the amount of projection of the separator rolls can be adjusted allowing for separation of both heavy and light weight media. It would further be advantageous to have a removable media dam wherein the position of the separator rolls can be automatically adjusted.